Lean Body Mass Increases following 12-Week Aerobic Training with Underwater but not Land Treadmill

Abstract

PURPOSE: To compare the changes in body composition following 12 weeks of exercise training using either a land treadmill (LTM) or underwater treadmill (UTM). METHODS: Forty-seven (men, n=19; women, n=28) sedentary, overweight/obese subjects participated in this investigation. The subjects' mean age, height, and weight were 44 yr, 171.7 cm, and 87.8 kg, respectively. Subjects were randomly assigned to exercise 3 times a week on either LTM (n=25) or UTM (n=22). Exercise intensities and durations were calculated such that subjects in both groups had the same caloric expenditure during each bout. The training regimen began at 250 kcal per bout, progressed to 500 kcal per bout by week 6, and remained at that level for the remainder of the study. Before and after training, weight (WT), percent body fat (%FAT), fat mass (FM), lean body mass (LBM), and regional fat and lean mass were assessed using dual-energy x-ray absorptiometry. Data were analyzed by 2x2 repeated measures ANOVA, with mode of exercise as the between subjects factor. Comparison wise error rate was set at α=0.05. RESULTS: Training was effective, as relative VO2MAX (Bruce GXT) increased from 27.8±5.4 to 31.3±5.9 mLO2·kg-1·min-1 after 12 weeks of training (p<0.0001). There was no difference in VO2MAX between groups. For WT, %FAT and FM, there was a training effect (p<0.01), however the differences between LTM and UTM were not significant (p>0.05). WT decreased from 87.8±18.0 to 86.8±17.2 kg, %FAT decreased from 39.8%±8.8 to 38.7%±8.9 and FM decreased from 33.6±10.6 to 32.4±10.8 kg. Changes in fat mass were mainly in the trunk (18.2±7.0 to 17.1±6.8 kg, p<0.01). LBM increased with UTM (51.1±12.7 to 51.9±12.4 kg, p<0.05) but not LTM. LBM increases were primarily seen in legs (LTM: 16.7±3.5 to 17.1±3.9 kg; UTM: 17.1±4.4 to 18.1±4.5 kg; p<0.01). There were no significant changes in lean or fat mass of other regions due to either mode of training. CONCLUSIONS: Aerobic exercise training on the UTM is able to elicit similar decreases in WT, %FAT, and FM as the LTM. However, LBM increases with UTM training, with gains seen mainly in the legs.